Heat treatment of composite bearings



Jan. 5, 1937. c. c. MOFFATT HEAT TREATMENT OF COMPOSITE BEARINGS Filed May 18, 1936 INVENTOR CHESTER CAMOFFATT A TTOR Y5 Graphite" .os- ;.10

Patented 5, 1937 UNITED STATES 2,067,061 Y I HEAT TREATMENT OF COMPOSITE r 1 1 BEARINGS 'Chester 0. Moifatt, Detroit, Mich assignor' to Bohn Aluminum & Mich., a corporation Application May 18,

' 5'Claims.

The invention relates tobearjrigsof that type 1 comprising a bearing surface or lining formed of a lead base alloy and a reinforcing shell on which this lining is mounted. 'It is the object of the in- 5 vention to obtain a bearing having improved characteristics with particular reference first, to

the wearing quality of the lining forming the bearing surface; second, as" to the strength of bondbetween the' ihing and the shell; third, as to resistance to fatigue. With this object in view the invention consists first, 'in a bearing having improved characteristics; and second, in the process through which these improved character-. istics are-attained.

In the drawing: 4 1 Figure 1 is a cross-section through a half-bearing of my improved construction;

Figure2 is a longitudinal section thereof slightly modified.

As above'stated, my improved bearing comprises a reinforcing shell of any suitable construction, but preferably of steel, and a liningformed of a lead base alloy. This lining comprises essentially a composition of tin, antimony and lead, in which the tin is the bonding element. The improved. characteristics of the bearing are not, however, due solely either to the structure or to the specific composition of the lining, but are chiefly due to the heat-treatment to which the bearings, are subjected after the original formation of the same. 7

The lead base alloy contains essentially'from 1 to 15% tin, from 5 to 20% antimony and the balance'mainly of lead. ,Other materials may be added thereto to,v obtain certain desirable characteristics, such as copper, graphite and arsenic.

Certain specific formulas which have been usedby me are as follows: 1 Per cent 1. Copper .15'- .65 Tin 825-1150 ,Antimony 11.50-47.00 Lead; .Q 70.00-79.00 Arsenic .10- .40 Graphite .04- .20

Percent 2 Copper .30 .75,

Tin 850-105 1 1 Antimo ny 1125 -15.25

w Lead 1 r 73.00 49.00 Arsenic .025- .10

Graphite.. v .04 ,10

e Percent 3. coppe ne; .10- .98

Till 7.00- 8,00 Antimony; 950-1150 Lead 80.00-85.00 Arse v .50

rass Corporation, Detroit,

of Michigan 1936; Serial No. 80,464 (01. us -1s) The function of the tin is to strengthen the bonding quality'of the alloy; the arsenic .is a

hardening agent; the graphite improves th antifriction character of the bearing surface; and the antimony resists attack by acids in the use of certain lubricatingoils. v

In the forming of. the bearing the steel shell developed such as A, Figure 1, has cast thereto the lining B which is bonded to the shell by a suitable material indicated at C. This bonding material may be either substantially puretin or an alloy oftin and lead or cadmium-nickel alloy, or any'other suitable material. For certain types of bearings, the shell A is provided with flanges D, as shown in Figure 2, and the bearing surface may either be on a single side of the shell or as indicated Y on the opposite sides at B and B Figure 2.

After thebearinghas been formed as above This heat treatment bearing-in an oil bath held in a suitable containerv and then heating the oil, as for-instance by placing the container within a thermostatically controlled electric ,fumace. The temperature is maintained at from 300 to 350 F. and for a period of time from 3 to Shouts. 'At the end of the heating period the container is removed from the furnace, but the bearing is still permitted to remain in the oil until cooled down. to normal temperature. 3 The improved characteristics of the heattreated bearing are. best shown by the following report of comparative tests that have been made of single half bearing structures lined with the bearing alloys specifically-set forth herein heattreated, and such structures without heat treat ment. -,J

' Bond tests Bearings, treated and untreated, semi-circular in shape, were flattened out under pressure until comparatively straight. The heat-treated bearings showed no cracking of the bearing metal and no separation of the bearing metal from the steel shell after 'the flattening, while the untreated bearings showed cracks in the bearing metal and separation of the bearing metal away from the steel' shell, after flattening.

lining-or separation of the bearing metal lining from the steel shell, while the unheat-treated bearings showed cracking and separation or, the

'50 Similar results were obtained using flanged lining from the shell, indicating improvement in physical characteristics solely through the heat treatment.

. Bearing wear tests Bearings, treated and untreated, were sub-- jected to tests in a bearing wear test machine in which bearings are run under conditions. approximating actual operating conditions, by means of a shaft revolving inside of bearings mounted in connecting rods, under adjustable speeds, bearing pressures; and temperatures.

Bearings under test are mum at normal speeds and'pressures and are finally subjected to abnormal conditions of speed and pressure calculated to break down the bearing.

In a series of tests on unheat-treated bearings, the average length of timeat breakdown speed was 8 to 10 hours, and the untreated bearings showed considerable cracking of the lining, which had become separated from the steel shell in some areas. Heat-treated bearings subjected to the same test ran from 18 to 20 hours, and were found to be superior in appearance and condition due to the beneficial effects of the heat treatment as described.

Summary Throughout, all the various tests on the heattreated and unheat-treated compositions mentioned, there has beendefinite data accumulated to indicate the superior bearing alloy structure and the bonding improvement of the heattreated bearings.

From the above, it is evident that bearings having their wearing surfaces formed of lead base alloy and when subjected to the heat treatment above described have greatly improved physical characteristics over similar structures not so treated. I

What I claim as my invention is:

1. In the manufacture of bearings comprising a reinforcing shell and a lining formed or a lead base alloy, the step of subjecting the bearing to heat-treat ent in which a uniform temperature of from to 350 F. is maintained for a period of from 3 to 20 hours and then gradually reduced to normal temperature.

2. In the manufacture of bearingscomprising a reinforcing shell and a lining formed of a composition having from 1 to 15% tin, 5 to 20% antimony and the balance mainly of lead, the step of subjecting the bearing to heat-treatment in which a uniform temperature of from 300 to 350 F. is maintained for a period of from 3 to 20 hours and then gradually reduced to normal temperature.

3. In the manufacture of bearings comprising a reinforcing shell and a lining formed of a composition having from 1 to 15% tin, 5 to antimony and the balance mainly of lead, the step of subjecting the bearing to heat-treatment in which a uniform temperature of approximately 350 F. is maintained for a period of from 3 to 6 hours and then gradually cooled.

4. In the manufacture of bearings comprising a reinforcing shell and a lining formed of a lead base alloy, the steps of placing the. bearing in a non-oxidizing oil within a container, subjecting the container and its contents to a unifrom 3 to 20 hours and then gradually reduced to normal temperature.

CHESTER C. MOFFATT. 

